Air pollution regulations for floating roof tanks are becoming increasingly stringent. The need for an improved circumferential seal for such tanks is real and urgent for the entire industry. A tank is deemed to violate regulations in some areas if the gap between the tank wall and the roof seal exceeds 1/8-inch for an accumulated length amounting to more than 5 percent of the tank circumference.
A primary problem with sealing the space between a floating roof and a circumferential wall of the tank resides in the presence of protuberances in the wall such as rivets, welds and the like. As the seal rises up and down with the floating roof, such protuberances cause gaps between the seal and the tank wall which allows the escape of pollutant vapors from the tank.